Patent GB-584140-A (GB)
Title: Improvements in or relating to the manufacture of low density alginic materials
IPC: C08J9/33
Filed: 1944-08-11
Abstract: Low density foamed materials are manufactured by preparing an alginate in the form of small grains of low density solidified foam and then binding the grains into a coherent solid by a matrix with which they are incorporated.  The grains may be prepared from a foam containing an alkali metal or ammonium alginate by first obtaining sheets, lengths or blocks of the foam which are gelled, optionally by the addition of calcium citrate to the foam and dried, the foam being subdivided into drops or fragments during or after either operation, for example by extrusion through nozzles, cutting into small pieces by rotating knives and then coagulating in a solution such as calcium acetate.  The grains are preferably washed after gelling and before drying.  The dry hardened grains are bonded together with a matrix which may be alginate foam such as that described in Specification 574,382, plaster of paris, cement, sealing wax, pitch, bitumen, polymethylmethacrylate or other thermoplastic or thermosetting resins, preferably by packing the grains into a container closed with a water-tight lid fitted with an escape valve for air, and forcing the fluid matrix up through the grains till all air is expelled, and then hardening the matrix.  Examples are given in which foams produced by adding saponin or the foaming agent sold under the Registered Trade Mark "Aphrosol" to an ammonium alginate solution are coagulated by means of a calcium acetate bath containing free lime. The grains thus formed are washed in running water and dried at 30-60 DEG  C. for 2-6 hours, then mixed with the matrix, moulded and dried. In a further example, a foam is produced with ammonium alginate solution, casein dissolved in ammonia, calcium carbonate and a foaming agent to which is added a solution of chromium sulphate, formaldehyde and sodium hexametaphosphate in water.  In this case a dilute coagulating bath is used and washing is unnecessary. Specification 560,317 also is referred to.ALSO:Low density foamed materials are manufactured by preparing an alginate in the form of small grains of low density solidified foam and then binding the grains into a coherent solid by a matrix with which they are incorporated.  The grains may be prepared from a foam containing an alkali metal or ammonium alginate by first obtaining sheets, lengths or blocks of the foam which are gelled, optionally by the addition of calcium citrate to the foam, and dried, the foam being subdivided into drops or fragments during or after either operation, for example by extrusion through nozzles, cutting into small pieces by rotating knives and then coagulating in a solution such as calcium acetate. The grains are preferably washed after gelling and before drying. The dry hardened grains are bonded together with a matrix which may be alginate foam such as that described in Specification 574,382, plaster of paris, cement, sealing wax, pitch, bitumen, polymethylmethacrylate or other thermoplastic or thermosetting resins, preferably by packing the grains into a container closed with a watertight lid fitted with an escape valve for air, and forcing the fluid matrix up through the grains till all air is expelled, and then hardening the matrix.  Examples are given in which foams produced by adding saponin or the foaming agent sold under the Registered Trade Mark "Aphrosol" to an ammonium alginate solution are coagulated by means of a calcium acetate bath containing free lime.  The grains thus formed are washed in running water and dried at 30-60 DEG C. for 2-6 hours, then mixed with the matrix, moulded, and dried.  In a further example a foam is produced with ammonium alginate solution, casein dissolved in ammonia, calcium carbonate and a foaming agent to which is added a solution of chromium sulphate, formaldehyde and sodium hexametaphosphate in water.  In this case a dilute coagulating bath is used and washing is unnecessary. Specification 560,317 also is referred to.